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@uitrit tatrs' @utenti @Hita GEORGE F. WILSON, OF EAST PROVIDENCE, RHODEISLAND, AND EBEN NORTON HOBSFORD, OF CAMBRIDGE, MASSACHUSETTS.

'Letters Patent lVol 75,339, dated .March 10, 1868.

IMPROVEMENT IN APPARATUS FOR GONGENTRATING ACID PHOSPHATE 0F LIME.

dlgs .Segnale aferra tu in tlgesvc Eaters nteut mit uniting aut nf thesmic.

TO ALL WHOM IT MAY-CONCERN l Be it known that we, GEORGE F. WILSON, ofEast Providence, in the county ot' Providence, and State of RhodeIsland, and EBEN NORTON Honsronn, of Cambridge, in the county ofMiddlesex, and State of Massachusetts, have invented a new and improvedMode of. Concentrating the Solution of Acid Phosphate of Lime; and weherebydeclare that'the following is a full and exact descriptionthereof, reference being had to the accompanying drawings, and to theletters of reference marked thereon.

The object of this our linvention is to facilitate the economical andcareful concentration of soluble acid phosphate of lime, and itsconversion, by the addition, from time to time, of neutral phosphate oflime, to an acid of the requisite strength und' qualities for domesticand other uses in the arts, as described in. Horsfords patents.

In order to conduct this process on a large scale, it is essential that,as evaporation proceeds, fresh quantities of liquor be added. It isnecessary to stir the liquor from time'to time, `as 'the neutralphosphate of lime or ground white bones are added, both to preventadhesion to the bottom ofthe -evaporating-vessel, and to facilitate theescape of carbonc-acid gas, which is contained in small quantity in theburned bones. This evolution of carbonic-acid gas is sometimes so rapidthat, taken in connection with the ebullition, if not carefully watched,liquor would be thrown out and lost. To prevent this loss, and also toprevent the adhesion of the acid to the bottom ofthe evaporating-vcssel,and generally to keep in the power of the operator the entire con trolof the' process, so as to produce a superior article, our experimentshave demonstrated the necessity of conducting the concentration in smalliron kettles lined with porcelain, and the further necessity of havingan independent re under each separate kettle, so that the fire may beregulated or instantly withdrawn, according to the condition of theliquor in each individual kettle. To accomplish these ends, we haveinvented the sys tem of boiler-furnaces, of which- Figure 1 presents aperspective view,

Figure 2 a. plan, and

Figure 3 and Figure 4 vertical sections, respectively, through L M and'RS of tig. 1.

The fire-pot o, over which the porcelain-lined kettle c is supported, isa short cast-iron hollow cylinder oi tube, z'z', (fig. 4,) with a ange,n n, projecting inward, for the support of the fire-brick lining A A. Weemploy also a short thick re-brick tube, having' the shape of the{ire-pot, and used in lieu of the encasing ironA tube.l The bottom ofthe tire-pot is a movable grate, with a handle, g, so as to be instantlywithdrawn, and the fire dropped into the ash-pit below, if necessary. Apassage-way or flue, b, at the top of the fire-peto, g. 3 and fig. 4,gives special communication from each fire-pot into and through thecommon ue T to the chimney, shown in iig. 2. The lire-pot is surmoun'tedby -a cast-iron plate, g q', having a hole Ato receive the kettle 7c.for evapo-A ration. p is thev ash-pit; g, the handle of the movablegrate. T, iig. 2 and g. 4, is the common ue, communicating on the onehand with the fire-pot ilues, and on Vthe other with the chimney.

In practical operation, one 'man attends a bench of twelve kettles. Theliquor is taken from a. tub or kiln,- marked to hold, between twolevels, one near the top, and the other near the bottom, one hundred andtwenty gallons by actual measure. The kettles are filled at thccommencement toltwo-thirds their capacity, covered withwooden ,covers,and placed `over the fires. As soon as boiling commences, the covers areremoved. The liquor is added as evaporation proceeds, and with theground white burned bones, the latter in calculated pro portion, varyinginversely with the specific gravity of the liquor. If the -heat becomestoo great, the kettle may be lifted from its place, and supportedfarther from the iire upon slender iron bars introduced under tho sides,while a draught over the top of the fire, -instead of through it,reduces the heat. The fire is renewed by,

lifting each kettle from' its seat and adding fresh coal. When theliquor has been concentrated to a'certain definite point, it isnecessary that no further concentration should take place. At this pointthe ire under the individual kettle may be dropped into the ash-pitbelow, and the concentration stopped. t this stage it requires to bestirred a short time to accomplish certain necessary chemical changes asit cools. To this end it is removed from the re-pot. Y Y

The arrangement above detailedk makes it possible for one operator to`attend a bench of twelve kettles, and

preserve the individuality of each kettle in the tirne and heat requiredfor the concentration and nishing-process due to each kettle.

The ire-pot, whether constructed of an iron cylinder lined withfire-brick, ns shown in fig. 4, or of a firebrick tube only, must hesurrounded with a space for air; otherwise the heat of the fire willbreak the furnace, and require constant repairs. The space is shown inthe drawings. I

We claim, and desire to secure by Letters Patent ci' the United Statesvl. The new and improved method or process of concentrating the acidphosphate-of-lime liquor by mean s of the apparatus constructed andarranged substantially as and for the purposes above described.

2. We claim also the use of metallic evaporatng-kettles lined withporcelain, for coneentratiifigy the solution of acid phosphate of lime,in the manufacture of Horsfords pulverulent phosphoric acid. i.

3. VWe claim the improved hre-pot, substantially as described, that isto say, consisting of fire-brick, lining a short metallic tube, or ashort continuous fire-brick tube, with a surrounding air-space, inconnection with thc use of the porcelain-lined kettle, for concentratingacid phosphate-oflime liquor. i

4. The nnovahle grate, in combination with the lire-pot andporcelain-lined kettle, substantially asand for thelpurpose abovedescribed.

5. The arrangement of the series or bench of single liettles abovedescribed, having a separate lire for each, in themanncr and for thepurpose set forth.

-GEO. F. WILSON, E. N. HORSFOR Witnesses:

WILLIAM Heinen', W. H. l\lcGrRENEP.Y.y

